The goal of this project is to institute a common protocol for advanced semen analysis at multiple clinical sites that will be used to analyze the relationship between the parameters of semen and fertility. The analytic strategy is not simply to characterize the semen of men whose fertility status is well-defined, but to develop new, predictive mathematical relationships between human semen quality and future fertility. The focus will be upon men who are infertility patients, with female partners who have no recognizable fertility problems. This group of men is most likely to provide a range in the parameters of semen needed to establish the mathematical models. First, a protocol for identification of this cohort of infertility patients will be applied. Then a standardized methodology at the multiple sites for analysis of sperm motion and morphology quality assurance. The parameters of sperm numbers, motion and morphology will be analyzed using familiar univariate and also new multivariate statistical approaches to screen for those measures of semen quality that are the most stable within men and which are determined with the greatest accuracy and precision. Then, a formal mathematical analysis of these data will be undertaken to establish the predictive ability of the advanced measures of semen quality with respect to future fertility.